The present invention generally relates to optical telecommunications. More specifically, the present invention relates to the optimization of optical fiber dispersion maps using slope-compensating optical fibers.
Light propagating within an optical fiber undergoes chromatic dispersion which causes the light to be delayed within the optical fiber. The specific amount of dispersion that light undergoes varies depending upon the wavelength of the light. The manner in which an optical fiber causes light to undergo chromatic dispersion is typically characterized by two parameters: (1) the dispersion at one specific wavelength, and (2) the dispersion slope, which indicates the extent to which dispersion varies as a function of light wavelength.
The dispersion slope of an optical fiber can significantly limit the usable bandwidth for a wavelength-division multiplex (WDM) system, which uses multiple information channels each having their own wavelength of light. Each information channel can accumulate its own amount of dispersion over the transmission link length. For example, in a WDM system having 10 Gb/s data-rate information channels, the information channels can accumulate a large amount of dispersion (e.g., more than xc2x13000 ps/nm) over long transmission distances, such as transoceanic transmission distances (e.g., 7000-10,000 km). When the accumulated dispersion is too large, the system performance is degraded due to intersymbol interference which, in turn, limits the system bandwidth.
Certain known dispersion maps compensate for the accumulated dispersion. In one such example, optical fiber segments having dispersions with opposite signs, can be alternatingly connected to define an optical link. In such a known dispersion map, the end-to-end path average dispersion remains low and fiber nonlinearities are suppressed.
A drawback associated with this type of dispersion map, however, is that the end-to-end path average dispersion varies significantly from wavelength to wavelength over long transmission distances due to the non-matching dispersion slopes of the two alternating optical fibers that define the overall optical link. This variation in the end-to-end path average dispersion (as a function of wavelength) limits the bandwidth of such a transmission system. Said another way, the bandwidth of a transmission system can only be expanded so far until the wavelength-based end-to-end path average dispersion limits the allowable bandwidth. Thus, a need exists to reduce the end-to-end path average dispersion below a tolerance threshold over a wide range of wavelengths. This need is particularly desirable with the prevalence of high-channel-count WDM systems.
An apparatus comprises operationally coupled optical fiber segments that define an optical sublink. The optical sublink has link spans including a first link span and a second link span. The first link span has an average dispersion with a magnitude greater than zero. The second link span has an average dispersion with a magnitude greater than zero. The optical sublink has an end-to-end dispersion less than an end-to-end dispersion tolerance limit.